Plant extract with antibacterial effect and preparation method thereof

Abstract

The invention relates to the technical field of bacteriostatic agents, in particular to a plant extract with a bacteriostatic effect and a preparation method thereof. The preparation method comprises the following steps: S1, mixing roxburgh rose roots, burdock, fructus forsythiae fruits, liquorice, cinnamon and papaya leaves, and crushing into mixed powder; s2, preparing an extraction auxiliary agent from carboxymethyl cellulose, lactoferrin and Tween-20; s3, adding the mixed powder into water, dipping, extracting and filtering to obtain a water extract and filter residues; s4, adding the filter residues into 95% ethanol, then adding an extraction aid, and extracting at 50-60 DEG C for 1-2 hours to obtain an alcohol extract; and S5, uniformly mixing the water extract and the alcohol extract, carrying out vacuum concentration, adding modified cyclodextrin, uniformly mixing, and carrying out spray drying to obtain the plant extract with the antibacterial effect. The plant extract is prepared by combining various plant components and the modified cyclodextrin, so that the antibacterial effect of the plant extract is remarkably improved, and the antibacterial durability of the plant extract is greatly prolonged.

Description

Technical Field

[0001] The invention relates to the technical field of antibacterial agents, and in particular to a plant extract with antibacterial effect and a preparation method thereof. Background Art

[0002] At present, the antiseptics and antibacterial agents used in the daily chemical industry are all traditional antiseptics and antibacterial agents synthesized by chemical synthesis. However, with the deepening of research, the controversy over traditional chemical antiseptics and antibacterial agents has gradually increased, and their potential dangers and long-term accumulated toxicity have attracted more and more attention. In terms of sterilization ability, alcohol disinfectants and phenol disinfectants have good effects on vegetative bacteria, but poor effects on spores and viruses. Quaternary ammonium salt compounds are only effective against Gram-positive bacteria; peroxide antibacterial agents are also difficult to promote and apply due to their safety and strong irritation. In terms of safety, peroxides, calcium hypochlorite, etc. have strong oxidizing or corrosive properties; alcohol disinfectants are flammable when exposed to open flames; chlorine-containing, bromine-containing and glutaraldehyde-containing disinfectants are not suitable for antibacterial treatment of skin or mucous membranes. Therefore, it is expected that new antiseptic ingredients that are safer, more stable, more efficient, mild, and natural and green will replace traditional antiseptics and antibacterial agents. Plant-derived antiseptic and antibacterial ingredients have become a research hotspot in the field of antiseptic and antibacterial replacement due to their unique biological activity, unique safety, non-irritation, and natural sources. Modern research has confirmed that the active ingredients in many natural plants have the characteristics of strong antibacterial activity, broad antibacterial spectrum, high safety, and small toxic and side effects.

[0003] Plant antibacterial ingredients have a wide range of raw materials, and are non-irritating, non-corrosive, non-toxic, stable in performance, and environmentally friendly. Compared with traditional disinfection and sterilization methods, they are more adaptable to the requirements of environmental hygiene when used in daily chemical products. Chinese patent CN201410106059.9 discloses a natural plant fungicide and its preparation method, which is prepared by mixing 60-80wt% of neem fruit extract, 3-20wt% of tea seed extract, and 10-30wt% of soapberry saponin alcohol extract, wherein the soapberry is squeezed to remove the core; the treated soapberry is soaked in saponin alcohol solution; heated and pulped; filtered to obtain the filtrate; alkaline protease is added for hydrolysis; concentrated, filtered, and the filtrate is obtained to obtain saponin alcohol solution for soapberry. The above technical scheme adopts all-natural plant extracts, and through scientific extraction, the extraction rate is effectively improved, the extracted product has good water solubility, and the reasonable combination of multiple different extracts can achieve better synergistic effects of bactericidal, antibacterial and antibacterial. It does not contain chemical additives, is non-toxic, harmless, has no side effects, is highly safe, and will not pollute the environment. It can be widely used in food, cosmetics, personal cleaning products, household cleaning products, daily chemical products and other fields.

[0004] However, the antibacterial ingredients of the above-mentioned fungicides are all plant extracts, and pure plant extract antibacterial agents may not be as strong as synthetic chemical antibacterial agents in antibacterial effect, and their durability may be shorter. Summary of the invention

[0005] In view of this, the present invention proposes a method for preparing a plant extract with antibacterial effect to solve the problem that the antibacterial effect and durability of a simple plant extract antibacterial agent are poor.

[0006] The technical solution of the present invention is achieved as follows: The present invention provides a method for preparing a plant extract with antibacterial effect, comprising the following steps:

[0007] S1, raw material pretreatment: mix the root of roxburghii, burdock fruit, forsythia fruit, liquorice, cinnamon and papaya leaf, grind them into powder, and pass through a 20-40 mesh sieve to obtain a mixed powder;

[0008] S2, preparation of an extraction aid: adding carboxymethyl cellulose to water, then adding lactoferrin, stirring at 60-70° C. for 1-2 h, then adding Tween-20, and continuing stirring for 1-2 h to obtain an extraction aid;

[0009] S3, primary extraction: adding the mixed powder into water, immersing and extracting, filtering, and obtaining a water extract and a filter residue;

[0010] S4, secondary extraction: add the filter residue into 95% ethanol, then add the extraction aid prepared in step S2, extract at 50-60°C for 1-2h, filter after the extraction is completed, and obtain an alcohol extract;

[0011] S5. Concentrate under reduced pressure and dry: Mix the water extract and the alcohol extract evenly, concentrate under reduced pressure to 1 / 4 of the volume to obtain a plant extract, then add modified cyclodextrin, mix evenly, and then spray dry to obtain a plant extract with antibacterial effect.

[0012] Specifically, in the present invention, an extract containing water-soluble antibacterial substances is obtained by a single extraction, and an extract containing fat-soluble antibacterial substances is obtained by a secondary extraction. The combination of the two extractions can more comprehensively extract various active ingredients in the plant, and obtain a broader spectrum of antibacterial effects. In step S5, the extract is mixed with modified cyclodextrin, wherein the modified cyclodextrin has an embedding effect, which can protect the active ingredients and improve stability. By spray drying, the modified cyclodextrin embeds the plant extract to form a microcapsule structure, which helps to achieve a sustained release effect and prolong the antibacterial time; at the same time, the silver ions loaded by the cyclodextrin can provide additional antibacterial effects, and synergistically improve the antibacterial effect with the plant extract.

[0013] On the basis of the above technical scheme, preferably, in step S1, the ingredients are, by weight, 30-50 parts of roxburghii root, 20-30 parts of burdock fruit, 25-40 parts of forsythia fruit, 15-30 parts of licorice, 10-20 parts of cinnamon bark, and 20-30 parts of papaya leaf.

[0014] In the present invention, the root of roxburghii contains a large amount of vitamin C and polyphenols, which can destroy bacterial cell membranes, inhibit bacterial growth, and have inhibitory effects on Staphylococcus aureus, Escherichia coli, Candida albicans, etc.; the burdock seed contains lignan compounds, which can interfere with the synthesis of bacterial cell walls, hinder bacterial growth, and have inhibitory effects on Staphylococcus aureus, Streptococcus pneumoniae, Escherichia coli, etc.; the forsythia fruit contains flavonoid compounds such as forsythiaside, which can inhibit the synthesis of bacterial proteins, and have inhibitory effects on Staphylococcus aureus, Candida albicans, Klebsiella pneumoniae, etc.; Licorice contains glycyrrhizic acid and flavonoids, which can destroy bacterial cell membranes, inhibit the synthesis of bacterial DNA and RNA, and have a broad-spectrum antibacterial effect on Staphylococcus aureus, Escherichia coli, Candida albicans, etc.; Cinnamon contains volatile oil components such as cinnamaldehyde, which can destroy bacterial cell membranes and cause leakage of cell contents, and has a good inhibitory effect on Staphylococcus aureus, Escherichia coli, Salmonella, etc.; Papaya leaves contain papain and polyphenols, which can destroy bacterial cell walls and cell membrane structures, and have an inhibitory effect on Staphylococcus aureus, Candida albicans, etc. The mixture of roxburghii root, burdock fruit, forsythia fruit, licorice, cinnamon and papaya leaves can inhibit a variety of bacteria, increasing the broad-spectrum antibacterial properties of the plant composition; each component attacks bacteria through different mechanisms, and this multiple mechanism can attack bacteria from multiple targets at the same time, greatly improving the antibacterial effect. In addition, different plant components have different release rates. For example, components with better water solubility (such as glycyrrhizic acid in licorice) are released faster, while fat-soluble components (such as cinnamaldehyde in cinnamon) are released slower. This differentiated release can achieve a sustained antibacterial effect and prolong the effective action time of the plant composition.

[0015] On the basis of the above technical solution, preferably, in step S2, the carboxymethyl cellulose, the lactoferrin, and the Tween-20 are 5-10 parts, 1-3 parts, and 0.5-1 parts, respectively, by weight.

[0016] Specifically, carboxymethyl cellulose, as a skeleton material, forms a three-dimensional network structure, which not only provides overall stability, but also provides attachment points for other ingredients and plant active substances; the antioxidant properties of lactoferrin can protect easily oxidized plant components, and its chelating ability may affect the extraction process that depends on certain metal ions, and it may also form a complex with plant polyphenols to increase stability; Tween-20, as a non-ionic surfactant, significantly improves the system's ability to dissolve and disperse hydrophobic compounds by reducing surface tension and forming micro-micelles. The above three components are compounded to form an extraction aid. The network structure provided by carboxymethyl cellulose provides a stable working environment for lactoferrin and Tween-20. The protective effect of lactoferrin extends to the active ingredients in the carboxymethyl cellulose network, while Tween-20 ensures the uniform distribution and full contact of various components in the entire system. The three components work synergistically to form a microenvironment that is conducive to the efficient extraction, protection and stabilization of a variety of plant active ingredients, thereby improving the extraction efficiency of effective ingredients.

[0017] On the basis of the above technical solution, preferably, in step S3, the mass ratio of the mixed powder to water is 1:20-30, and after immersion for 1 hour, extraction is performed at 70-80° C. for 2-3 hours.

[0018] On the basis of the above technical solution, preferably, in step S4, the mass ratio of the filter residue to 95% ethanol is 1:15-25, and the added amount of the extraction aid is 4-6% of the mass of the filter residue.

[0019] Based on the above technical solution, preferably, in step S5, the preparation method of modified cyclodextrin includes:

[0020] S11, dissolving β-cyclodextrin in water, adding sodium hydroxide solution, mixing evenly, then adding epichlorohydrin to the system, stirring at a constant temperature of 40-45° C. for 2-3 hours, to obtain a cyclodextrin polymer;

[0021] S12. Dissolve the cyclodextrin polymer and silver nitrate in water, mix them evenly by ultrasonication, and react at 60-80°C for 4-7h to obtain a reaction solution; add hexadecyltrimethylammonium bromide to the reaction solution, mix them evenly, and then add methanol, crystallize them at room temperature overnight, collect the precipitate by centrifugation, and obtain modified cyclodextrin.

[0022] Specifically, in step S11, β-cyclodextrin is activated under alkaline conditions, the hydroxyl group is ionized, and then epichlorohydrin is used as a cross-linking agent to undergo a ring-opening reaction with the activated cyclodextrin molecules to form a larger molecular network structure, thereby obtaining a cyclodextrin polymer with a higher molecular weight and more functional groups, thereby improving the embedding capacity and stability of cyclodextrin. The macromolecular network structure formed by the cross-linking reaction not only improves the physical stability, but also reduces the diffusion rate, which is conducive to achieving a sustained release effect; the polymerized cyclodextrin retains the original ring structure, the overall number of cavities is significantly increased, and a variety of cavity sizes are formed, which can then embed the active ingredients in the plant extract, such as polyphenols, flavonoids, etc. This embedding effect can protect these active ingredients, prolong their half-life, and achieve slow release, thereby prolonging their action time. In step S12, the cyclodextrin polymer serves as an organic ligand, and its functional groups such as hydroxyl and ether bonds can form coordination bonds with silver ions, thereby loading the silver ions onto the cyclodextrin polymer. Silver ions have antibacterial effects and can produce synergistic antibacterial effects with natural antibacterial components in plant extracts (such as glycyrrhizic acid in licorice and cinnamaldehyde in cinnamon), thereby enhancing the overall antibacterial ability; hexadecyltrimethylammonium bromide serves as a surfactant and can be adsorbed on the surface of cyclodextrin through electrostatic and hydrophobic interactions, thereby increasing the stability and dispersibility of the modified cyclodextrin.

[0023] On the basis of the above technical solution, preferably, in step S11, the concentration of the sodium hydroxide solution is 0.08-0.12 mol / L, and the mass ratio of epichlorohydrin to β-cyclodextrin is (0.2-0.3):1.

[0024] On the basis of the above technical solution, preferably, in step S12, the mass ratio of the cyclodextrin polymer to silver nitrate is (1-3):1, and the added amount of the hexadecyltrimethylammonium bromide is 1-10% of the mass of the cyclodextrin polymer.

[0025] On the basis of the above technical solution, preferably, in step S5, the mass ratio of the modified cyclodextrin to the plant extract is 1:(2-3).

[0026] In another aspect, the present invention provides a plant extract with antibacterial effect, wherein the plant extract with antibacterial effect is prepared by the above-mentioned preparation method. The plant extract with antibacterial effect can be used in daily chemical products, such as household cleaners.

[0027] The plant extract with antibacterial effect and the preparation method thereof of the present invention have the following beneficial effects compared with the prior art:

[0028] (1) The plant extract is prepared by combining multiple plant components with modified cyclodextrin, wherein the multiple plant components provide multiple antibacterial mechanisms, and the modified cyclodextrin provides an efficient inclusion and sustained-release platform. The synergistic effect not only significantly improves the antibacterial effect of the plant extract, but also greatly prolongs its durability. The finally obtained plant extract has strong and lasting antibacterial activity, high stability, good bioavailability, high safety, and can be widely used in the field of daily chemicals;

[0029] (2) Using roxburghii root, burdock fruit, forsythia fruit, liquorice, cinnamon and papaya leaves as antibacterial active ingredients, the above plants contain a variety of active ingredients, such as flavonoids, polyphenols, terpenes and alkaloids, which work together to inhibit bacteria through different mechanisms (such as destroying bacterial cell walls, inhibiting protein synthesis, interfering with bacterial metabolism, etc.); at the same time, the synergistic effect between the various plant ingredients enhances the broad-spectrum antibacterial effect and can cope with a variety of pathogenic microorganisms;

[0030] (3) Carboxymethyl cellulose, lactoferrin and Tween-20 are used to form an extraction aid, wherein carboxymethyl cellulose provides a stable network structure, lactoferrin plays an antioxidant and protective role, and Tween-20 enhances the solubility and dispersibility of hydrophobic compounds. The three components work synergistically to create a microenvironment that is conducive to the efficient extraction, protection and stabilization of a variety of plant active ingredients, which not only improves the extraction efficiency, but also protects the oxidizable and sensitive active substances, ensuring the high quality and stability of the extract;

[0031] (4) The modified cyclodextrin obtained by cross-linking with epichlorohydrin and modification with silver nitrate and hexadecyltrimethylammonium bromide not only has a stronger inclusion capacity, but also achieves a sustained release of the antibacterial effect. The modified cyclodextrin can effectively encapsulate and protect the plant active ingredients to prevent their oxidation and degradation, while gradually releasing these ingredients through a sustained release mechanism. In addition, the introduced silver ions and plant components form a synergistic antibacterial system: the silver ions first quickly exert an immediate antibacterial effect, and then the slowly released plant active ingredients continue to exert an antibacterial effect, thereby significantly extending the overall antibacterial time of the product. This dual antibacterial mechanism not only enhances the antibacterial effect, but also greatly improves the persistence of antibacterial effect, effectively solving the problem of poor antibacterial persistence of simple plant extracts. DETAILED DESCRIPTION

[0032] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] The carboxymethyl cellulose was purchased from Beijing Prein Biochromatography Technology Co., Ltd., with a CAS number of 9000-11-7; lactoferrin was purchased from Hubei Wei's Chemical Reagent Co., Ltd., with a lactoferrin content of 95-102%; Tween-20 was purchased from Nanjing Bermuda Biotechnology Co., Ltd.; and β-cyclodextrin was purchased from Chengdu Wanxiang Hongrun Biotechnology Co., Ltd.

[0034] Example 1

[0035] This embodiment provides a plant extract with antibacterial effect and a preparation method thereof, comprising the following steps:

[0036] S1, raw material pretreatment: 45g of roxburghii root, 25g of burdock fruit, 35g of forsythia fruit, 25g of licorice, 15g of cinnamon bark and 25g of papaya leaf were mixed and crushed into powder, and passed through a 20-40 mesh sieve to obtain a mixed powder;

[0037] S2, preparation of extraction aid: 8g carboxymethyl cellulose was added to water, followed by 2g lactoferrin, stirred at 65°C for 1.5h, then 0.8g Tween-20 was added, and stirring was continued for 1-2h to obtain extraction aid;

[0038] S3, primary extraction: add the mixed powder into water with a solid-liquid ratio of 1:25, soak for 1 hour and then extract at 75°C for 2.5 hours. After the extraction is completed, filter to obtain a water extract and a filter residue;

[0039] S4, secondary extraction: add the filter residue to 95% ethanol, with a solid-liquid ratio of 1:20, then add 5% of the weight of the filter residue as an extraction aid, extract at 55°C for 1.5h, filter after the extraction is completed, and obtain an alcohol extract;

[0040] S5. Concentrate and dry under reduced pressure: Mix the water extract and the alcohol extract evenly, concentrate under reduced pressure to 1 / 4 of the volume to obtain a plant extract, then add modified cyclodextrin and mix evenly, the mass ratio of modified cyclodextrin to plant extract is 1:2.5, followed by spray drying (inlet air temperature 160°C, atomization pressure 0.3-0.4MPa) to obtain a plant extract with antibacterial effect.

[0041] The preparation method of modified cyclodextrin comprises the following steps:

[0042] S11, dissolving 10 g of β-cyclodextrin in 500 mL of water, adding 4 mL of 0.1 mol / L sodium hydroxide solution, mixing evenly, then adding 2.5 g of epichlorohydrin to the system, stirring at a constant temperature of 45° C. for 2.5 h, adjusting the pH to neutral, precipitating with alcohol, washing, and drying to obtain a cyclodextrin polymer;

[0043] S12. Dissolve 10 g of cyclodextrin polymer and 3 g of silver nitrate in 250 mL of pure water, mix evenly by ultrasonication, and react at 40°C for 5.5 h to obtain a reaction solution; add 0.6 g of hexadecyltrimethylammonium bromide to the reaction solution, mix evenly, then add 50 mL of methanol, keep at room temperature overnight, centrifuge (speed 10000 rpm, time 20 min) to collect the precipitate, and dry to obtain modified cyclodextrin.

[0044] Example 2

[0045] This embodiment provides a plant extract with antibacterial effect and a preparation method thereof, comprising the following steps:

[0046] S1, raw material pretreatment: 30g of roxburghii root, 20g of burdock fruit, 25g of forsythia fruit, 15g of licorice, 10g of cinnamon and 20g of papaya leaf were mixed and crushed into powder, and passed through a 20-40 mesh sieve to obtain a mixed powder;

[0047] S2, preparation of extraction aid: 5g carboxymethyl cellulose was added to water, followed by 1g lactoferrin, stirred at 60°C for 1h, then 0.5g Tween-20 was added, and stirring was continued for 1h to obtain extraction aid;

[0048] S3, primary extraction: add the mixed powder into water with a solid-liquid ratio of 1:20, soak for 1 hour and then extract at 70°C for 2 hours. After the extraction is completed, filter to obtain a water extract and a filter residue;

[0049] S4, secondary extraction: add the filter residue to 95% ethanol, with a solid-liquid ratio of 1:15, then add 4% of the weight of the filter residue as an extraction aid, extract at 50°C for 1h, filter after the extraction is completed, and obtain an alcohol extract;

[0050] S5. Concentrate and dry under reduced pressure: Mix the water extract and the alcohol extract evenly, concentrate under reduced pressure to 1 / 4 of the volume to obtain a plant extract, then add modified cyclodextrin and mix evenly, the mass ratio of modified cyclodextrin to plant extract is 1:2, followed by spray drying (inlet air temperature 140°C, atomization pressure 0.3-0.4MPa) to obtain a plant extract with antibacterial effect.

[0051] The preparation method of modified cyclodextrin comprises the following steps:

[0052] S11, dissolving 10 g of β-cyclodextrin in 500 mL of water, adding 3 mL of 0.08 mol / L sodium hydroxide solution, mixing evenly, then adding 2 g of epichlorohydrin to the system, stirring at a constant temperature of 40° C. for 2 h, adjusting the pH to neutral, precipitating with alcohol, washing, and drying to obtain a cyclodextrin polymer;

[0053] S12. Dissolve 10 g of cyclodextrin polymer and 2 g of silver nitrate in 200 mL of pure water, mix evenly by ultrasonication, and react at 35°C for 4 h to obtain a reaction solution; add 0.1 g of hexadecyltrimethylammonium bromide to the reaction solution, mix evenly, then add 20 mL of methanol, keep at room temperature overnight, centrifuge (speed 8000 rpm, time 15 min) to collect the precipitate, and dry to obtain modified cyclodextrin.

[0054] Example 3

[0055] This embodiment provides a plant extract with antibacterial effect and a preparation method thereof, comprising the following steps:

[0056] S1, raw material pretreatment: 50g of roxburghii root, 30g of burdock fruit, 40g of forsythia fruit, 30g of licorice, 20g of cinnamon and 30g of papaya leaf were mixed and crushed into powder, and passed through a 20-40 mesh sieve to obtain a mixed powder;

[0057] S2, preparation of extraction aid: 10g carboxymethyl cellulose was added to water, followed by 3g lactoferrin, stirred at 70°C for 2h, then 1g Tween-20 was added, and stirring was continued for 2h to obtain extraction aid;

[0058] S3, primary extraction: add the mixed powder into water with a solid-liquid ratio of 1:30, soak for 1 hour and then extract at 80°C for 3 hours. After the extraction is completed, filter to obtain a water extract and a filter residue;

[0059] S4, secondary extraction: add the filter residue to 95% ethanol, with a solid-liquid ratio of 1:25, then add 6% of the weight of the filter residue as an extraction aid, extract at 60°C for 2h, filter after the extraction is completed, and obtain an alcohol extract;

[0060] S5. Concentrate and dry under reduced pressure: Mix the water extract and the alcohol extract evenly, concentrate under reduced pressure to 1 / 4 of the volume to obtain a plant extract, then add modified cyclodextrin and mix evenly, the mass ratio of modified cyclodextrin to plant extract is 1:3, followed by spray drying (inlet air temperature 180°C, atomization pressure 0.3-0.4MPa) to obtain a plant extract with antibacterial effect.

[0061] The preparation method of modified cyclodextrin comprises the following steps:

[0062] S11, dissolving 10 g of β-cyclodextrin in 500 mL of water, adding 5 mL of 0.12 mol / L sodium hydroxide solution, mixing evenly, then adding 3 g of epichlorohydrin to the system, stirring at a constant temperature of 45° C. for 3 h, adjusting the pH to neutral, precipitating with alcohol, washing, and drying to obtain a cyclodextrin polymer;

[0063] S12. Dissolve 10 g of cyclodextrin polymer and 4 g of silver nitrate in 300 mL of pure water, mix evenly by ultrasonication, and react at 45°C for 7 h to obtain a reaction solution; add 1 g of hexadecyltrimethylammonium bromide to the reaction solution, mix evenly, then add 100 mL of methanol, keep at room temperature overnight, centrifuge (speed 10000 rpm, time 25 min) to collect the precipitate, and dry to obtain modified cyclodextrin.

[0064] Example 4

[0065] This embodiment provides a plant extract with antibacterial effect and a preparation method thereof, comprising the following steps:

[0066] S1, raw material pretreatment: 35g of roxburghii root, 20g of burdock fruit, 30g of forsythia fruit, 20g of liquorice, 14g of cinnamon bark and 28g of papaya leaf were mixed and crushed into powder, and passed through a 20-40 mesh sieve to obtain a mixed powder;

[0067] S2, preparation of extraction aid: 7 g of carboxymethyl cellulose was added to water, followed by 2.5 g of lactoferrin, stirred at 60° C. for 2 h, then 0.7 g of Tween-20 was added, and stirring was continued for 1 h to obtain extraction aid;

[0068] S3, primary extraction: add the mixed powder into water with a solid-liquid ratio of 1:28, soak for 1 hour and then extract at 70°C for 3 hours. After the extraction is completed, filter to obtain a water extract and a filter residue;

[0069] S4, secondary extraction: add the filter residue to 95% ethanol, with a solid-liquid ratio of 1:18, then add 5% of the weight of the filter residue as an extraction aid, extract at 60°C for 1h, filter after the extraction is completed, and obtain an alcohol extract;

[0070] S5. Concentrate and dry under reduced pressure: Mix the water extract and the alcohol extract evenly, concentrate under reduced pressure to 1 / 4 of the volume to obtain a plant extract, then add modified cyclodextrin and mix evenly, the mass ratio of modified cyclodextrin to plant extract is 1:2, followed by spray drying (inlet air temperature 180°C, atomization pressure 0.3-0.4MPa) to obtain a plant extract with antibacterial effect.

[0071] The preparation method of modified cyclodextrin comprises the following steps:

[0072] S11, dissolving 10 g of β-cyclodextrin in 500 mL of water, adding 4.5 mL of 0.11 mol / L sodium hydroxide solution, mixing evenly, then adding 3 g of epichlorohydrin to the system, stirring at a constant temperature of 40° C. for 3 h, adjusting the pH to neutral, precipitating with alcohol, washing, and drying to obtain a cyclodextrin polymer;

[0073] S12. Dissolve 10 g of cyclodextrin polymer and 3.5 g of silver nitrate in 200 mL of pure water, mix evenly by ultrasonication, and react at 45 °C for 4 h to obtain a reaction solution; add 0.7 g of hexadecyltrimethylammonium bromide to the reaction solution, mix evenly, then add 30 mL of methanol, keep at room temperature overnight, centrifuge (speed 8000 rpm, time 25 min) to collect the precipitate, and dry to obtain modified cyclodextrin.

[0074] Comparative Example 1

[0075] This comparative example provides a plant extract with antibacterial effect and a preparation method thereof, comprising the following steps:

[0076] S1, raw material pretreatment: 45g of roxburghii root, 25g of burdock fruit, 35g of forsythia fruit, 25g of licorice, 15g of cinnamon bark and 25g of papaya leaf were mixed and crushed into powder, and passed through a 20-40 mesh sieve to obtain a mixed powder;

[0077] S2. Primary extraction: add the mixed powder into water with a solid-liquid ratio of 1:25, soak for 1 hour and then extract at 75°C for 2.5 hours. After the extraction is completed, filter to obtain a water extract and a filter residue;

[0078] S3, secondary extraction: add the filter residue to 95% ethanol, with a solid-liquid ratio of 1:20, then add 5% Tween-20 of the filter residue mass, extract at 55°C for 1.5h, filter after the extraction is completed, and obtain an alcohol extract;

[0079] S4, vacuum concentration and drying: the water extract and the alcohol extract are mixed evenly, and the mixture is concentrated under reduced pressure to 1 / 4 of the volume to obtain a plant extract. Then, cyclodextrin is added and mixed evenly. The mass ratio of cyclodextrin to plant extract is 1:2.5. The mixture is then spray dried (inlet air temperature 160°C, atomization pressure 0.3-0.4MPa) to obtain a plant extract with antibacterial effect.

[0080] Comparative Example 2

[0081] This comparative example provides a plant extract with antibacterial effect and a preparation method thereof, comprising the following steps:

[0082] S1, raw material pretreatment: 45g of roxburghii root, 25g of burdock fruit, 35g of forsythia fruit, 25g of licorice, 15g of cinnamon bark and 25g of papaya leaf were mixed and crushed into powder, and passed through a 20-40 mesh sieve to obtain a mixed powder;

[0083] S2, preparation of extraction aid: 8g carboxymethyl cellulose was added to water, followed by 2g lactoferrin, stirred at 65°C for 1.5h, then 0.8g Tween-20 was added, and stirring was continued for 1-2h to obtain extraction aid;

[0084] S3, primary extraction: add the mixed powder into water with a solid-liquid ratio of 1:25, soak for 1 hour and then extract at 75°C for 2.5 hours. After the extraction is completed, filter to obtain a water extract and a filter residue;

[0085] S4, secondary extraction: add the filter residue to 95% ethanol, with a solid-liquid ratio of 1:20, then add 5% of the weight of the filter residue as an extraction aid, extract at 55°C for 1.5h, filter after the extraction is completed, and obtain an alcohol extract;

[0086] S5. Concentrate and dry under reduced pressure: Mix the water extract and the alcohol extract evenly, concentrate under reduced pressure to 1 / 4 of the volume to obtain a plant extract, then add cyclodextrin and mix evenly, the mass ratio of cyclodextrin to plant extract is 1:2.5, followed by spray drying (inlet air temperature 160°C, atomization pressure 0.3-0.4MPa) to obtain a plant extract with antibacterial effect.

[0087] Comparative Example 3

[0088] This comparative example provides a plant extract with antibacterial effect and a preparation method thereof, comprising the following steps:

[0089] S1, raw material pretreatment: 45g of roxburghii root, 25g of burdock fruit, 35g of forsythia fruit, 25g of licorice, 15g of cinnamon bark and 25g of papaya leaf were mixed and crushed into powder, and passed through a 20-40 mesh sieve to obtain a mixed powder;

[0090] S2, preparation of extraction aid: 8g carboxymethyl cellulose was added to water, followed by 2g lactoferrin, stirred at 65°C for 1.5h, then 0.8g Tween-20 was added, and stirring was continued for 1-2h to obtain extraction aid;

[0091] S3, primary extraction: add the mixed powder into water with a solid-liquid ratio of 1:25, soak for 1 hour and then extract at 75°C for 2.5 hours. After the extraction is completed, filter to obtain a water extract and a filter residue;

[0092] S4, secondary extraction: add the filter residue to 95% ethanol, with a solid-liquid ratio of 1:20, then add 5% of the weight of the filter residue as an extraction aid, extract at 55°C for 1.5h, filter after the extraction is completed, and obtain an alcohol extract;

[0093] S5. Concentrate and dry under reduced pressure: Mix the water extract and the alcohol extract evenly, concentrate under reduced pressure to 1 / 4 of the volume to obtain a plant extract, then add modified cyclodextrin and mix evenly, the mass ratio of modified cyclodextrin to plant extract is 1:2.5, followed by spray drying (inlet air temperature 160°C, atomization pressure 0.3-0.4MPa) to obtain a plant extract with antibacterial effect.

[0094] The preparation method of modified cyclodextrin comprises the following steps:

[0095] S11. Dissolve 10 g of β-cyclodextrin in 500 mL of water, add 4 mL of 1.0 mol / L sodium hydroxide solution, mix well, then add 2.5 g of epichlorohydrin to the system, stir at a constant temperature of 45°C for 2.5 h, adjust the pH to neutral, precipitate with alcohol, wash and dry to obtain modified cyclodextrin.

[0096] Comparative Example 4

[0097] This comparative example provides a plant extract with antibacterial effect and a preparation method thereof, comprising the following steps:

[0098] S1, raw material pretreatment: 45g of roxburghii root and 35g of forsythia fruit were mixed and crushed into powder, and passed through a 20-40 mesh sieve to obtain a mixed powder;

[0099] S2, preparation of extraction aid: 8g carboxymethyl cellulose was added to water, followed by 2g lactoferrin, stirred at 65°C for 1.5h, then 0.8g Tween-20 was added, and stirring was continued for 1-2h to obtain extraction aid;

[0100] S3, primary extraction: add the mixed powder into water with a solid-liquid ratio of 1:25, soak for 1 hour and then extract at 75°C for 2.5 hours. After the extraction is completed, filter to obtain a water extract and a filter residue;

[0101] S4, secondary extraction: add the filter residue to 95% ethanol, with a solid-liquid ratio of 1:20, then add 5% of the weight of the filter residue as an extraction aid, extract at 55°C for 1.5h, filter after the extraction is completed, and obtain an alcohol extract;

[0102] S5. Concentrate and dry under reduced pressure: Mix the water extract and the alcohol extract evenly, concentrate under reduced pressure to 1 / 4 of the volume to obtain a plant extract, then add modified cyclodextrin and mix evenly, the mass ratio of modified cyclodextrin to plant extract is 1:2.5, followed by spray drying (inlet air temperature 160°C, atomization pressure 0.3-0.4MPa) to obtain a plant extract with antibacterial effect.

[0103] The preparation method of modified cyclodextrin comprises the following steps:

[0104] S11, dissolving 10 g of β-cyclodextrin in 500 mL of water, adding 4 mL of 0.1 mol / L sodium hydroxide solution, mixing evenly, then adding 2.5 g of epichlorohydrin to the system, stirring at a constant temperature of 45° C. for 2.5 h, adjusting the pH to neutral, precipitating with alcohol, washing, and drying to obtain a cyclodextrin polymer;

[0105] S12. Dissolve 10 g of cyclodextrin polymer and 3 g of silver nitrate in 250 mL of pure water, mix evenly by ultrasonication, and react at 40°C for 5.5 h to obtain a reaction solution; add 0.6 g of hexadecyltrimethylammonium bromide to the reaction solution, mix evenly, then add 50 mL of methanol, keep at room temperature overnight, centrifuge (speed 10000 rpm, time 20 min) to collect the precipitate, and dry to obtain modified cyclodextrin.

[0106] Performance Testing

[0107] The plant extracts prepared in the examples and comparative examples were mixed with water to prepare a solution, wherein the content of the plant extract was 3wt.%, and the antibacterial performance was tested according to the "ASTM E2149-13a Experimental method for determining the activity of antimicrobial agents under dynamic conditions", and the test bacteria were Escherichia coli, Staphylococcus aureus, Candida albicans and Salmonella, and the antibacterial effects were tested after 2h, 10h and 24h, respectively. The test results are shown in Tables 1 and 2.

[0108] Table 1 Antibacterial performance test

[0109]

[0110] Table 2 Antibacterial performance test

[0111]

[0112]

[0113] As shown in Table 1, the plant extracts prepared by the present invention have good antibacterial effects on a variety of bacteria, and the antibacterial rates are all above 98%, with high antibacterial effects and long antibacterial duration.

[0114] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a plant extract having an antibacterial effect, characterized in that: The following steps are involved: S1, raw material pretreatment: mix the root of roxburghii, burdock fruit, forsythia fruit, liquorice, cinnamon and papaya leaf, grind them into powder, and pass through a 20-40 mesh sieve to obtain a mixed powder; S2, preparation of an extraction aid: adding carboxymethyl cellulose to water, then adding lactoferrin, stirring at 60-70° C. for 1-2 h, then adding Tween-20, and continuing stirring for 1-2 h to obtain an extraction aid; S3, primary extraction: adding the mixed powder into water, immersing and extracting, filtering, and obtaining a water extract and a filter residue; S4, secondary extraction: add the filter residue into 95% ethanol, then add the extraction aid prepared in step S2, extract at 50-60°C for 1-2h, filter after the extraction is completed, and obtain an alcohol extract; S5. Concentrate under reduced pressure and dry: Mix the water extract and the alcohol extract evenly, concentrate under reduced pressure to 1 / 4 of the volume to obtain a plant extract, then add modified cyclodextrin, mix evenly, and then spray dry to obtain a plant extract with antibacterial effect.

2. The method for preparing a plant extract with antibacterial effect according to claim 1, characterized in that: In step S1, the ingredients include 30-50 parts of roxburghii root, 20-30 parts of burdock fruit, 25-40 parts of forsythia fruit, 15-30 parts of licorice, 10-20 parts of cinnamon bark, and 20-30 parts of papaya leaf, by weight.

3. The method for preparing a plant extract with antibacterial effect according to claim 1, characterized in that: In step S2, the carboxymethyl cellulose, lactoferrin and Tween-20 are 5-10 parts, 1-3 parts and 0.5-1 parts respectively by weight.

4. The method for preparing a plant extract with antibacterial effect according to claim 1, characterized in that: In step S3, the mass ratio of the mixed powder to water is 1:20-30, and after immersion for 1 hour, extraction is performed at 70-80° C. for 2-3 hours.

5. The method for preparing a plant extract with antibacterial effect according to claim 1, characterized in that: In step S4, the mass ratio of the filter residue to 95% ethanol is 1:15-25, and the amount of the extraction aid added is 4-6% of the mass of the filter residue.

6. The method for preparing a plant extract with antibacterial effect according to claim 1, characterized in that: In step S5, the preparation method of modified cyclodextrin includes: S11, dissolving β-cyclodextrin in water, adding sodium hydroxide solution, mixing evenly, then adding epichlorohydrin to the system, stirring at a constant temperature of 40-45° C. for 2-3 hours, to obtain a cyclodextrin polymer; S12. Dissolve the cyclodextrin polymer and silver nitrate in water, mix them evenly by ultrasonication, and react them at 35-45°C for 4-7h to obtain a reaction solution; add hexadecyltrimethylammonium bromide to the reaction solution, mix them evenly, and then add methanol, keep them at room temperature overnight, collect the precipitate by centrifugation, and obtain modified cyclodextrin.

7. The method for preparing a plant extract with antibacterial effect according to claim 6, characterized in that: In step S11, the concentration of the sodium hydroxide solution is 0.08-0.12 mol / L, and the mass ratio of epichlorohydrin to β-cyclodextrin is (0.2-0.3):

1.

8. The method for preparing a plant extract with antibacterial effect according to claim 6, characterized in that: In step S12, the mass ratio of the cyclodextrin polymer to silver nitrate is 1:(0.2-0.4), and the amount of cetyltrimethylammonium bromide added is 1-10% of the mass of the cyclodextrin polymer.

9. The method for preparing a plant extract with antibacterial effect according to claim 1, characterized in that: In step S5, the mass ratio of the modified cyclodextrin to the plant extract is 1:(2-3).

10. A plant extract with antibacterial effect prepared by the preparation method according to any one of claims 1 to 9.

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